In an long term evolution-advanced (LTE-A) technology, a carrier aggregation (CA) technology has been introduced to broaden the bandwidth of a mobile communication system. To overcome the bandwidth limitation due to the increase of mobile data traffic, the 3rd generation partnership project (3GPP) standard has recently adopted licensed-assisted access (LAA), which sets a part of carriers according to the CA to a frequency band for wireless fidelity (Wi-Fi). Before the discussion on the LAA, the discussion on long term evolution-unlicensed (LTE-U) is underway. The LTE-U is a non-standard technology that uses the frequency band for Wi-Fi as the long term evolution (LTE) frequency band.